Investigating the manufacture of TDR burials waveguides and evaluation of their application in soil moisture estimation

Knowledge of the moisture content is important for making decision for seeding, irrigation, soil management and other soil, water and natural resource projects. Conventional methods such as gravimetric or neutronmetry methods for measuring soil moisture are time consuming and sensitive application, respectively. The Time Domain Reflectometry is commonly known as TDR, is a new method for determining volumetric water content. The probes of TDR are two types, connector and burial types. Use of connector probe for soil moisture measurement in the coarse sand and in the natural resource lands is disappointed, so use of burial probes are advised. But those are expensive. Therefore those must be manufactured. Manufactory and Calibration of burial probes is the main objectives of this study. After choosing cable testers, BNC port and suitable stainless steel for two parallel metallic rods, the burial probes were manufactured, and then those calibrated. To calibrate manufactured type of probes, measurements were made using the TRACE system (soil moisture equipment corp.) with the conventional rod-type probes (or standard type) and manufactured types of probes in three difference types of soil texture classes, these were sandy loam, loam and silty clay, respectively. The bulk densities for sandy loam, loam and silty clay texture were, 1.66, 1.47, 1.30 gr/cm3, respectively. There was a good linear correlation between the two estimates. The highest relation determination was observed in sandy loam texture in 10 ns capture windows. Calibration equations for sandy loam, loam and silty clay texture were y= 1.1013x - 0.3661, y= 0.9761x - 1.0193 and y= 0.9961x - 0.0933, respectively.